It has become popular for many designs of the common safety bicycle to use suspension systems, mainly designs of the `mountain bicycle`. Present suspension systems used on these bicycles have technical difficulties in achieving light weight systems that do not have problems that affect the bicycle's performance. Many of the current front and rear suspension systems do not allow adjustment for optimizing the bicycle for different terrain's, and those that do require a long down time to perform these adjustments. Most front suspensions are also difficult to maintain.
The problems for most bicycle suspension systems stem from the fact that they are essentially modified motorcycle suspensions. Common front suspension designs that use telescopically compressing cylinders do not maintain accurate geometric alignment of the front wheel during suspension travel. These suspension systems also typically have poor lateral and fore/aft stiffness, that is they allow `slop` in the system, and have initial stiction to overcome in handling small irregularities, all problems that degrade performance. These front suspension systems also need to be adjusted for the riders size and style of riding, or they can perform badly. Many front suspension designs require regular maintenance. Adjusting and maintaining these front suspensions can be very time consuming, since the system has to be completely disassembled, and most require special tools and knowledge to do so. Also, since these types of suspensions use multiple redundant tubes that slide in and around each other, they have a large amount of redundant weight.
Rear suspension systems in use today that use motorcycle style swing arms, while allowing a large amount of rear wheel travel, deprive the bicycle of propulsive energy. The systems that do not use a motorcycle style swing arm concept, commonly called "pivotless" suspensions, do not absorb much of the propulsive energy, but they do not allow a large amount of rear wheel travel. Present rear swing arm style suspensions also tend to add a great deal of weight to the bicycle frame, in the form of redundant frame members, and linkage members that are not part of the suspension system but are needed to go around sections of the bicycle frame to connect the suspension to the frame.
Rear suspensions that use the motorcycle swing arm concept are typically influenced by drive torque, thus they absorb the propulsive energy. There are several variations that are presently in use, some absorb power at all times, some absorb more power while the rider is seated, some absorb more power when the rider is sprinting, or climbing, and is out of the saddle.
Rear bicycle suspensions that do not use a motorcycle style swing arm design usually have curved and/or sprung seat stays, and chain stay's that do not pivot on bearing assemblies. These are commonly called "pivotless" suspension systems. This style of rear suspension does not greatly absorb the propulsive energy intended for the rear wheel, however, they do not allow large amounts of rear wheel travel and usually cannot be adjusted for ride height and/or shock and spring rates.
The inventor observed that, while the concepts of bicycle suspensions and fully suspended bicycles, do have their merits, the technical difficulties that degrade the overall performance of the common suspension systems used in bicycles needed to be overcome. Improved suspension systems needed to be designed for the bicycle, that will solve the problems that plague current bicycle suspension designs, lower the complexity and weight of the suspension systems, increase the functionality, and simplify the serviceability and adjustability. An improved rear bicycle suspension needed to be developed that would reduce the drive power absorbed while allowing a large amount of rear wheel travel, and a front suspension system needed to be developed that would decrease the weight, and eliminate the stiction and alignment problems, of the common telescopically compressing cylinder suspension forks.
The suspension systems envisioned by the inventor use a parallelogram design concept that will allow a large amount of travel for both the front and rear wheels, lower the number of suspension members, compared to many common suspension systems, and increase the reliability and simplicity of maintenance and adjustment. The parallelogram suspension system will allow a filly suspended bicycle to weigh very close, if not equal, to the weight of a non-suspended bicycle. A parallelogram suspension system can be used on the front or rear wheels individually or together, on a safety bicycle, recumbent bicycle, tandem bicycle, tricycle, and any other type of presently existing and yet to be developed human powered vehicle. The only absolute requirement for a parallelogram suspension system is that it uses at least two main suspension members with the centers of the fore and aft pivot points aligned in a geometric parallelogram.
Parallelogram suspension systems will improve front wheel performance over current designs, will allow the rear wheel to ride over surface abnormalities with little affect on the propulsive energy being transmitted to the rear wheel, will allow a bicycle to be fully suspended using only one shock and spring sub-assembly unit for both wheels, and can allow any suspension system to be quickly and fully adjusted for spring rate, shock rate, ride height and suspension travel, thus allowing the bicycle to be optimized for different riders, terrain's, and riding situations.
Front suspensions made with a parallelogram design will not suffer from geometric alignment changes when the wheel transverses over surface irregularities or when the ride height is changed, can use a single low maintenance shock and spring unit rather than multiple compression units, and will not suffer from looseness or stiction, all problems with the common telescopic compression style of suspension fork. A parallelogram front suspension design can weigh the same as a similar non-suspended design, except for the weight of the shock and spring members, and will make it possible to use weight saving carbon-fiber forks and tubes, and other such weight saving improvements, thus making it possible to have a front suspension system weigh very close to a non-suspended front fork.